Nyeng Tine Bisballe, Nordsmark Marianne, Hoffmann Lone
a Department of Medical Physics , Aarhus University Hospital , Denmark.
b Department of Oncology , Aarhus University Hospital , Denmark.
Acta Oncol. 2015;54(9):1467-73. doi: 10.3109/0284186X.2015.1068449. Epub 2015 Jul 29.
Some oesophageal cancer patients undergoing chemotherapy and concomitant radiotherapy (chemoRT) show large interfractional anatomical changes during treatment. These changes may modify the dose delivered to the target and organs at risk (OARs). The aim of the presenwt study was to investigate the dosimetric consequences of anatomical changes during treatment to obtain criteria for an adaptive RT decision support system.
Twenty-nine patients were treated with chemoRT for oesophageal and gastro-oesophageal junction cancer and set up according to daily cone beam computed tomography (CBCTs) scans. All patients had an additional replanning CT scan at median fraction number 10 (9-14), which was deformably registered to the original planning CT. Gross tumour volumes (GTVs), clinical target volumes (CTVs) and OARs were transferred to the additional CT and corrected by an exwperienced physician. Treatment plans were recalculated and dose to targets and OARs was evaluated. Treatment was adapted if the volume receiving 95% of the prescribed dose (V95%) coverage of CTV decreased > 1% or planning target volume (PTV) decreased by > 3%.
In total, nine adaptive events were observed: All nine were triggered by PTV V95% decrease > 3% [median 11% (5-41%)] and six of these were additionally triggered by CTV V95% decrease > 1% [median 5% (2-35%)]. The largest discrepancies were caused by interfractional baseline or amplitude shifts in diaphragm position (n = 5). Mediastinal (n = 6), oesophageal (n = 6) and bowel filling changes (n = 2) caused the remainder of the changes. For patients with dosimetric changes exceeding the adaptation limits, the discrepancies were confirmed by inspecting the daily CBCTs. In 31% of all patients, heart V30Gy increased more than 2% (maximum 5%). Only minor changes in lung dose or liver dose were seen.
Target coverage throughout the course of chemoRT treatment is compromised in some patients due to interfractional anatomical changes. Dose to the heart may increase as well.
一些接受化疗联合放疗（同步放化疗）的食管癌患者在治疗期间出现较大的分次间解剖结构变化。这些变化可能会改变输送到靶区和危及器官（OARs）的剂量。本研究的目的是调查治疗期间解剖结构变化的剂量学后果，以获得自适应放疗决策支持系统的标准。
29例食管和胃食管交界癌患者接受同步放化疗，并根据每日锥形束计算机断层扫描（CBCT）进行摆位。所有患者在中位分次次数10次（9 - 14次）时额外进行了一次重新计划CT扫描，该扫描与原始计划CT进行了变形配准。大体肿瘤体积（GTVs）、临床靶体积（CTVs）和OARs被转移到额外的CT上，并由经验丰富的医生进行校正。重新计算治疗计划并评估靶区和OARs的剂量。如果接受处方剂量95%（V95%）的CTV覆盖体积减少>1%或计划靶体积（PTV）减少>3%，则调整治疗。
总共观察到9次自适应事件：所有9次均由PTV V95%减少>3%触发[中位值11%（5 - 41%）]，其中6次还由CTV V95%减少>1%触发[中位值5%（2 - 35%）]。最大的差异是由分次间膈肌位置的基线或幅度变化引起的（n = 5）。纵隔（n = 6）、食管（n = 6）和肠腔充盈变化（n = 2）导致了其余的变化。对于剂量学变化超过调整限度的患者，通过检查每日CBCT证实了差异。在所有患者中，31%的患者心脏V30Gy增加超过2%（最大5%）。仅观察到肺部剂量或肝脏剂量有轻微变化。
由于分次间解剖结构变化，一些患者在同步放化疗治疗过程中的靶区覆盖受到影响。心脏剂量也可能增加。
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